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IAUC 4341: 1987A

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                                                  Circular No. 4341
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM    Telephone 617-495-7244/7440/7444

     P. Crane, European Southern Observatory; and M. Leventhal,
Bell Telephone Laboratories, telex: "Of the six peaks in the
spectrum reported by Gry et al. (IAUC 4324), three were also present
on Mar. 3 (IAUC 4330) and might correspond to lines in the Lyman
series of positronium, the bound state of an electron and a positron.
Comparison of these lines (239.2, 202.4, 187.2 nm) with the
rest wavelengths of positronium (Ly alpha, 243.0; beta, 205.0; delta,
189.8 nm) indicates a blueshift of about 4200 +/- 450 km/s, the scatter
being comparable to the estimated uncertainty (+/- 0.3 nm) in the
observed wavelengths.  One would expect the strongest line to be
that at 239.2 nm, and indeed it is.  Ly gamma would be expected to
appear at 191.7 nm, and there is reason to believe that the failure
to detect it is due to its falling in an inopportune position
on the IUE spectrograph.  The probability that these lines fall at
the appropriate wavelengths by chance is < 1 in 10**4."
     N. Suntzeff, Cerro Tololo Interamerican Observatory, telexes:
"SN 1987A has stopped its rapid color evolution and appears to be
in a 'plateau' phase, similar to type II supernovae after maximum
light.  This evolution in color and brightness has been 5-10 times
more rapid than for other type II objects discussed by Barbon et
al. (1979, A.Ap. 72, 287).  The CTIO nightly spectra show that the
Balmer P-Cyg profiles are decreasing in strength relative to other
emission features such as Fe II.  M. Hamuy has obtained the following
Cousins-system photometry: Mar. 5.1 UT, V = 4.42, B-V = +1.08,
U-B = +1.55, V-R = +0.47, R-I = +0.13; 6.1, 4.38, +1.17, +1.63,
+0.48, +0.14; 7.1, 4.35, +1.23, -, -, -; 8.1, 4.33, 1.31, -, -, -;
9.1, 4.30, +1.35, +1.81, +0.51, +0.18; 10.1, 4.28, +1.38, +1.85,
+0.52, +0.19; 11.1, 4.26, +1.42, +1.89, +0.54, +0.20.  Ultraviolet
CCD observations by S. G. Djorgovski with the 1.5-m and 4-m
telescopes on Mar. 8 showed diffuse [O II] 372.7-nm emission in the
field that may be associated with 30 Dor; there is no sign of an H
II or other nebula in which the SN is embedded.  At 373.4 nm (6.0-
nm filter) there is a companion about 2" to the southwest of the SN."
     Total visual magnitude estimates: Mar. 11.41, 4.1 (T.
Beresford, Adelaide, South Australia); 11.42, 4.3 (R. H. McNaught,
Coonabarabran, N.S.W.).
     Corrigendum.  IAUC 4332, line 5 from foot.  For  U-B = -0.03
read  R-I = -0.03

1987 March 12                  (4341)              Brian G. Marsden

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